JPS6054575A - Automatic dimming device for image pickup using liquid crystal filter - Google Patents

Abstract

PURPOSE:To make the automatic dimming of an incident light quantity to a photoreceptor element possible and to effectively prevent a blooming phenomenon by controlling the transmitting light quantity of a liquid crystal filter in accordance with the level of an output signal from the photoreceptor element. CONSTITUTION:An optical image formed on the image pickup surface of a solid- state image pickup element 4 is converted into electric signals corresponding to each picture element and supplied to a video processing section 6 and, at the same time, supplied to an A/D converter 13 where the electric signals are converted into digital signals in accordance with their level. The digital signals are converted into 4-bit signals by an encoder 14 and the 4-bit signals are added to a multiplexer 15 where the 4-bit signals are switched four pieces at a time and inputted into a liquid crystal driving circuit 12. The output voltage of the circuit 12 is applied to a liquid crystal filter 8 installed to the front face of the image pickup element 4 and the light shielding section of the filter 8 is controlled. Thus the incident light quantity is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an automatic light adjustment device for imaging using a liquid crystal filter that can automatically set the light reception level suitable for imaging.

[Technical Blueprint of the Invention and Its Problems] In recent years, imaging devices using solid-state imaging devices, such as television cameras and endoscopes, have become widely used.

When using the above-mentioned solid-state image sensor, if the amount of incident light that is reflected by the object and forms the object image on the imaging surface formed by arranging the light-receiving elements of the solid-state image sensor via the objective lens is locally large. There is a so-called blooming phenomenon in which the image cannot be displayed correctly on the playback screen because the excessive amount of light is superimposed on the original signal that is separately imaged on the side of the adjacent light receiving elements. arise.

If the photosensitive characteristics of the solid-state image carrier are lowered to prevent the above-mentioned blooming phenomenon from occurring, it becomes impossible to image the subject under dim lighting.

Therefore, in the past, the amount of incident light was adjusted manually or mechanically with a diaphragm or the like using a monitor, but the response speed was slow and the blooming phenomenon could not be sufficiently prevented.

Another disadvantage is that if there are locally bright and dark areas mixed in one screen when an image is captured, if the amount of light received is uniformly adjusted using the aperture, it will not be possible to diagnose the dark areas in detail. was there.

[Object of the Invention] The present invention has been made in view of the above-mentioned points, and provides an imaging method using a liquid crystal filter that can effectively prevent the blueing phenomenon and can also handle cases where dark areas and bright areas coexist. The purpose is to provide an automatic light control device for

[Summary of the Invention] The present invention provides a dimming means that controls the amount of light transmitted through the liquid crystal filter according to the level of the signal output from the light receiving element, thereby controlling the amount of light of each pixel. It is configured to automatically adjust the amount of light incident on a light receiving element or a continuous group of light receiving elements on an appropriate scale.

[Embodiments of the invention] Hereinafter, the present invention will be specifically explained with reference to the drawings.

1 to 3 relate to a first embodiment of the present invention, FIG. 1 shows an imaging device to which the first embodiment is applied, FIG. 2 shows a circuit configuration of a liquid crystal drive circuit, and FIG. Figure 3 shows a liquid crystal filter.

As shown in FIG. 1, in an imaging device 1 equipped with an automatic light adjustment device according to the first embodiment, an objective lens 3 for image formation is disposed in a lens barrel 2, and the image formation position of the objective lens 3 is A solid R such as a C0D (charge-coupled device) with its imaging surface facing
An image element 4 is provided.

A large number of light receiving elements are regularly arranged on the imaging surface of the solid-state image sensor 4, and each pixel in the optical image formed on the R image surface is converted into an electrical signal corresponding to the pixel,
The clock signal applied from the signal reading circuit 5 allows the output signals of the light receiving elements arranged in each horizontal line to be sequentially extracted, for example. Three primary color filters arranged in a mosaic pattern (not shown) are attached to the image pickup surface, and by passing through the three primary color filters, each color pixel signal in the three primary colors is captured, and after being amplified by a preamplifier (not shown), it is sent to the video processing section 6. After being further amplified, the sample and hold circuit in the video processing section 6 separates each color pixel signal according to the pixel signal, and after passing through a color amplifier, the horizontal and vertical synchronizing signals are superimposed, and each color signal of the three primary colors R, G, B is displayed on a color television receiver 7 for a monitor.

By the way, a liquid crystal filter 8 forming the first embodiment is disposed in front of the three primary color filters.

The liquid crystal filter 8 regularly covers each of the light-receiving elements arranged on the imaging surface with square blocks of 9 nm (indicated by thick solid lines) as shown in FIG. m rows of 9 nm blocks are formed by sticking transparent electrodes over the entire surface on one side, and the other side is formed so as to be divided into two, for example, in the horizontal direction (horizontal direction) and the vertical direction (vertical direction). The four divided electrode parts are 10 nm-+.

10 nm-2, I Q nm-3, and 10 nm-t are formed.

Each of these divided electrodes 101m-cx (α-1, 2, 3, 4
) are led out by lead wires llnm, and connected to each output terminal 12nm-c, H of the liquid crystal drive circuit 12.

Note that by applying a voltage to each of the electrode portions 1Q nm, the light-transmitting portion before application becomes a light-shielding portion.

By the way, the signal output from the solid-state image sensor 4 and amplified by the preamplifier is sent to the A/D converter 1 according to its level.
3, it is converted into a 2-bit digital Ild+62, and the encoder 14 converts it into a binary digital fid+.
dr is connected to be applied from four output terminals to four switching input terminals of the multiplexer circuit 15 as an O (low level) or 1 (high level) signal.

The above-mentioned digital ff1d+d2 is converted into, for example, 'o o'→''0000', '01' in the encoder 14.
→”ooo i”, “io”→”0011”,
The data is converted from "11" to "0111", and the multiplexer circuit 15 switches every four pieces and inputs them to the liquid crystal drive circuit 12. Note that the multiplex circuit 15 is formed by using, for example, four multiplexers in parallel.

The signal output from the multiplexer circuit 15 is used, for example, as a sampling pulse, and when this signal is at a high level, the hold circuit 16v-a (v=1
．． 2. ... ; α = 1.2.3.4) at its output end 1
The level output from 2nLr is maintained at the high level potential of the battery 17. Note that this holding is performed for a time approximately equal to one frame period which is then selected by the multiplexer circuit 15.

The multiplexer circuit 15 is configured such that the output terminals of nm groups are sequentially switched by a switching signal outputted from a switching circuit 18 in synchronization with the tarok signal of the signal reading circuit 5. Here, nm (nXm) is the number of pixels, that is, the number of light receiving elements of the solid-state image sensor 4 or the number of blocks in the liquid crystal filter 8. The number of lines of the switching signal is sufficient to sequentially switch nm groups.

The above hold circuit 16v (is the multiplexer circuit 15
When a high-level sampling pulse is applied to each control terminal, the high-level signal is applied to the corresponding electrode section of the liquid crystal filter 8 until it is selected by the multiplexer circuit 15. is applied to make that part a light shielding part, while no sampling pulse is applied to the control end (in other words, a low level sampling pulse).
Regardless of the previous value, the signal output is at a low level until the next selection by the multiplexer circuit 15, and the electrode portion thereof maintains a transparent portion.

That is, the level of the pixel signal output from the light receiving element is A/
If the digital amount corresponding to the level after D conversion is large, the number of high-level signal lines output from the four output terminals of the encoder 14 will increase, and the number of high-level signal lines output from the four output terminals of the encoder 14 will increase. A number of voltages corresponding to the high level are applied to each of the four electrode portions of each block in the liquid crystal filter 8, and the electrode portions are held in the light shielding portion.

In other words, depending on the amount of incident light received, a light control means is formed that enlarges the light shielding portion when the amount of light is too large, and does not block the light when the amount of light is small.

The operation of the first embodiment of the present invention configured in this manner will be described below.

The objective lens 3 forms an image of the object on the image plane of the solid-state image sensor 4. This image is decomposed into pixels by each light receiving element, and is converted into an electric signal (pixel signal) corresponding to the pixel. They are sequentially output together with a clock signal.The output signals are amplified with low noise by a preamplifier, separated into three primary color signals R, G, and B by a video processing section 6, and displayed on a color television 7 for a monitor. With the stiffness,
The light is automatically controlled by the light control means as follows.

That is, the signal amplified by the preamplifier is converted into a digital quantity by the A/D converter 13 according to the signal level, and converted by the encoder 14 into a digital quantity whose level becomes high by the number corresponding to the digital quantity. and are sequentially input to the multiplexer circuit 15.

The multiplexer circuit 15 is sequentially switched in synchronization with the signal extraction of each light receiving element, and for example, the first coarse is selected in response to the output signal of the light receiving element in the first row and first column. When the signal '0001' is output, a high level sampling pulse is applied only to the hold circuit 161-4 in FIG.
The drive voltage output from a is kept at a high level, and the other hold circuits 16+, -+, 16+ -2, 16+
-3 connected to each output @12++ −+ , 12+
The output levels of +-2 and 12n-3 are held at low level.

Therefore, in the block 911 in the first row and first column of the liquid crystal filter 8, the electrode portion jon-a becomes a light-shielding portion by the applied voltage, and the remaining portion maintains a light-transmitting portion. Similarly, N in each block 9 of the liquid crystal filter 8 in front of the other light receiving element is determined according to the signal level of the other light receiving element.
The amount of light received at the extreme portions is also adjusted.

The light indication received by each light receiving element is controlled every frame period, and the control state is maintained within that period. ) The light will be automatically adjusted to the effective amount of light received.

In the present invention, the portion of the liquid crystal filter 8 that covers the corresponding light receiving element is adjusted for each pixel according to the level of the signal output from each light receiving element as described above, and in synchronization with the output of that signal. Since the light-shielding area (light-transmitting area) is controlled, for example, even if the amount of light incident on a certain light-receiving element is locally too large on the R image plane corresponding to the same screen, it can be quickly detected by the signal output. In the light-transmitting part of the part where the light is incident on the light-receiving element, the light-transmitting part can be enlarged to prevent the occurrence of a blue sky, and at the same time, it is possible to prevent the light from becoming too bright in the next frame period.
Can be displayed with moderate brightness and contrast).

As mentioned above, the amount of light received by each pixel can be quickly controlled, so if dark areas and excessively bright areas coexist on the same screen, and the overall amount of incident light is reduced using an aperture, etc., the state of the dark area can be identified. However, even in cases where bright areas tend to cause blooming if you do not stop down,
The present invention can adequately cope with this problem. Furthermore, since a means for adjusting the light receiving aperture is formed, the dynamic range can be greatly expanded. Therefore, even if a solid-state image sensor 4 with a narrow dynamic range is used, the range field can be compressed and imaged. In this case, if necessary, the compressed image can be restored and displayed on the reproduction side, and a more faithful reproduced image can be obtained.

FIG. 4 shows the shape of the N-pole portion of a liquid crystal filter in a second embodiment of the present invention.

In the liquid crystal filter 21 in this embodiment, each block of 9 nm has a square electrode portion 22 nm-+, and the electrode portion 22 nm-2 is formed with the outer periphery of the electrode portion 22 nm-+ sequentially shaped like a frame. 2211111-3, 22n
m-4. (Only the reference numeral indicates the one in the first row and first column, that is, n=m=1.) When the liquid crystal filter 21 is used, substantially the same effect can be obtained.

It should be noted that the present invention is not limited to what has been described above,
For example, in the block 911m that covers each pixel (each light-receiving element) in the liquid filters 8 and 21, a W II section with a large number of rough divisions is formed, so that the LIA can be set to an appropriate amount of light even at a more precise level. You can also.

Note that the division when forming the electrode part is not limited to equal division, but may be uneven, or a part where no electrode part is formed (a part that is not always light-shielded) may be formed. or,
The order of the light-shielding parts can also be arbitrarily determined.

Furthermore, in the above embodiment, each light-receiving element corresponding to each pixel can be controlled independently, but the present invention is not limited to this. It is also possible to commonly control every two blocks connected to each other or every several tens of blocks, that is, every connected light receiving element group. In this way, the number of lead wires to the electrode portion can be significantly reduced. In this case, each pixel has a close relationship with its nearest neighbor, so by simplifying it, the amount of light received is close to that in the case of dimming for each pixel (or each light receiving element). Control (dimming) may be possible.

When sharing the blocks every several blocks to several tens of blocks, it may be common in a continuous line in the horizontal or vertical direction, or in a square shape.

It may be divided into rectangular shapes or other suitable scales and shared.

In this case, each one of the shared light-receiving element groups is used as a representative signal to be A/D converted, or a signal obtained by adding or integrating the signals of each light-receiving element forming each group is A/D-converted. It can also be used as a representative of a signal.

It is obvious that the present invention can be applied not only to a general R imaging device as described above, but also to an imaging means for observation in an endoscope having an illumination means.

Note that the A/D converter 13 that converts the signal level from the light receiving element into a digital quantity does not necessarily need to have good linearity, and instead of using the A/D converter 13 and encoder 14, , a plurality of comparators each having a different reference level may be provided in parallel, and the output thereof may be input to the multiplexer circuit 15.

Furthermore, the liquid crystal drive circuit 12 is not limited to the above-mentioned configuration, and may also be formed using a latch or the like.

Furthermore, although the above description is directed to high-level light shielding, it is clear that a configuration may also be adopted in which light is shielded at low level.

In the above-described embodiment, in the case of a color image carrier, deviations in the white balance can be prevented by controlling the brightness of the pixels of these three colors in common according to the arrangement of the three primary color filters in a mosaic pattern or the like. Furthermore, it is also possible to adopt a configuration in which the adjacent image signals of the three primary colors are added together before being converted into digital quantities, and the resulting signal is averaged by an integrating circuit to perform dimming.

In the case of these color images, for example, after passing through an integrating circuit, a color correction amplifier is inserted in the middle of the automatic light control circuit to convey images with more faithful hues without changing the white balance. Or it can be made playable.

It is clear that the present invention is applicable not only to color imaging but also to monochrome imaging.

Effects of the Invention As described above, according to the present invention, the transmission of light through the liquid crystal filter in the portion that covers the corresponding light-receiving element depends on the signal level output according to the amount of light received by the light-receiving element. Since the amount of light is controlled, the blooming phenomenon can be prevented and the amount of received light can be automatically set to be suitable for image transport or observation.

Furthermore, it is possible to form an imaging means that can significantly widen the dynamic range and reproduce more faithfully.

[Brief explanation of the drawing]

Figures 1 to 3 relate to the first embodiment of the present invention.
The figure shows an imaging device equipped with the first embodiment, FIG. 2 is a block diagram showing the vicinity of the liquid crystal drive circuit, FIG. 3 is an explanatory diagram showing the liquid crystal filter, and FIG. It is an explanatory view showing a liquid crystal filter. 1... Imaging device 3... Objective lens 4... Solid-state image sensor 5... Signal reading circuit 6... Video processing unit 7... Color television receiver 8.21... Liquid crystal filter 9u+...9r++n...Block 1Qnm-1,
=1Of1m-4,22nnl-+, ・=221m
-a... Electrode section 12... Liquid crystal drive circuit 13... A/D converter 14... Encoder 15...
...Multiplexer circuit 16v-+, ...16v-a...Hold circuit 18
...switching circuit

Claims (3)

[Claims] (1) The optical image of the subject is formed by the imaging lens on the light receiving elements arranged on the imaging surface of the solid-state image sensor, and the signal corresponding to each pixel output from each light receiving element is captured. In an imaging device capable of reproducing images, the amount of light received by each light receiving element or a group of consecutive light receiving elements on a moderate scale can be variably adjusted by controlling the application of a voltage in front of the imaging surface. dimmer means for controlling the amount of transmitted light of a portion of the liquid crystal filter that covers the light receiving element based on a signal output from the light receiving element or a group of light receiving elements; An automatic light control device for imaging using a liquid crystal filter, characterized in that: (2) The light control means forms liquid crystal driving signals of a high level number or a low level number according to the level of the output horn signal of the light receiving element, and covers the liquid crystal 1 driving signal with the output horn signal of the light receiving element. An automatic light control device for a Shu image using a liquid crystal filter according to claim 1, characterized in that it is formed by applying a plurality of electric currents t1 of the liquid crystal filter portion. (3) The liquid crystal filter according to claim 1 is used, wherein the light control means functions in a cycle of one frame period in which signals from all the light receiving elements of the solid-state image carrier are read. Automatic light control device for imaging.